CN112920396B - Synthesis method of hydroxyl-terminated high-oxygen-content high-flexibility azide polymer - Google Patents

Abstract

The invention relates to a method for synthesizing a hydroxyl-terminated azide polymer with high oxygen content and high flexibility. The polymer is hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane (PADXL). PADXL is synthesized by cationic ring-opening polymerization of 2-halomethyl-1,3-dioxolane (XDXL) to obtain a high-oxygen polyether containing carbon-halogen bonds, and then through macromolecular nucleophilic The substitution reaction uses sodium azide to azidize the carbon-halogen bond to obtain hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane. The method is safe and efficient, and the obtained azide polymer has the characteristics of high energy, high oxygen content, low glass transition temperature, and controllable molecular weight. able adhesive.

Description

A kind of synthetic method of terminal hydroxyl high oxygen content high flexibility azide polymer

technical field

The invention belongs to the field of macromolecules, and in particular relates to a synthesis method and application of an azide polymer with high oxygen content at terminal hydroxyl groups and high flexibility.

Background technique

Driven by the needs of aerospace and national defense, high energy has become the main development trend of solid propellants. As the core component of the propellant formulation, the binder plays an important role in supporting the solid filler and maintaining the mechanical properties. Recent studies have shown that replacing traditional hydroxyl-terminated polybutadiene (HTPB) and ethylene oxide-tetrahydrofuran copolyether (PET) binders with energetic binders is an important way to increase the energy level of propellants.

At present, the azide polymers that have been widely studied mainly include polyazide glycidyl ether (GAP), poly 3-methyl-3-azidomethyl oxybutane (PAMMO), poly 3,3-bis-azidomethyl Oxetane (PBAMO), etc. Although GAP has the problem of poor mechanical properties, especially low-temperature mechanical properties, GAP has the following advantages: high energy and high burning rate, cheap and easy-to-obtain raw materials, simple synthesis process, and large-scale production. Therefore, GAP is still the most widely studied azide polymer. Most of the work in recent years has focused on improving the mechanical properties of GAP through modification. For example, Byoung Sun Min et al. used GAP and polyethylene glycol (PEG) as prepolymers, and IPDI and N-100 as mixed curing agents to prepare PEG-modified GAP adhesives. When the PEG content is 30 wt %, the tensile strength is 2.17MPa, the elongation at break is 253%, and the modulus is 6.1MPa (Propellants, Explosives, Pyrotechnics, 2008, 33, 131–138). Luo Yunjun's research group at Beijing Institute of Technology selected HTPB with a molecular weight of 2840 and a hydroxyl value of 40.39mg/g and GAP for mixed curing, and discussed the influence of preparation parameters on the mechanical properties. When the R value is 1.7 and the ratio of GAP/HTPB/trimethylolpropane/1,4-butanediol hydroxyl content is 1:1:1.1:0.46, the tensile strength is 1.43MPa and the elongation at break is 382%. (New Chemical Materials, 2009, 37, 66–68). Gao Jianbin and others from the 42 Institute of Aerospace Science and Technology prepared GAP/polymethyl methacrylate (PMMA) interpenetrating network. Due to the hydrogen bond between the urethane bond in the GAP elastomer and the carbonyl group of the PMMA side chain, it stretches The strength is significantly improved, and when the PMMA content is 40%, the tensile strength can reach 10MPa (Chemical Propellants and Polymer Materials, 2003, 1, 31–34). However, this method usually requires the addition of a non-energetic component with better mechanical properties, which will reduce the energy level of GAP.

Compared with GAP, the number of carbon atoms in the main chain of PAMMO is increased, and its mechanical properties are better. After forming a copolymer with BAMO, it has an energy level equivalent to that of GAP, so it has been widely studied. For example, Zhang et al. used BAMO-AMMO alternating block thermoplastic elastomers as binders to prepare composite solid propellant samples. The detonation heat can reach 6256 kJ/kg, the tensile strength at room temperature is 1.56MPa, and the elongation at break The ratio is 20%, and the performance is better than that of GAP-based composite propellants with the same solid content (Propellants, Explosives, Pyrotechnics, 2012, 37, 235–240). However, the synthesis route of PAMMO is more complex and costly than that of GAP, and its high melt viscosity is not conducive to processing, which restricts its practical application.

Therefore, it is of practical significance to design and develop a synthetic method for azide polymers with high oxygen content and high flexibility to improve the practicability of current energetic adhesives.

Contents of the invention

Aiming at the problems existing in the prior art, the invention provides a method for synthesizing an azide polymer with high oxygen content in terminal hydroxyl groups and high flexibility. The method is safe and efficient, and the obtained azide polymer has the characteristics of high energy, high oxygen content, low glass transition temperature, and controllable molecular weight. able adhesive.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A method for synthesizing a highly flexible azide polymer with high oxygen content at the terminal hydroxyl group, using an indirect two-step method:

The first step is cationic ring-opening polymerization: add initiator, catalyst, reaction solvent and monomer to the reaction vessel, and release hydrogen ions (cations) after the initiator reacts with the catalyst, and the hydrogen ions attack the electron-rich oxygen in the monomer atom, induce ring opening of the monomer, and polymerize at a certain temperature to obtain a polymer;

The second step is the azidation reaction: in a dipolar solvent, the halogen atom in the carbon-halogen bond on the side chain of the polymer prepared in the first step is replaced by the azidation reagent under the action of the catalyst to obtain the terminal hydroxyl group Azide polymer with high oxygen content and high flexibility.

Further, the monomer in the first step is 2-halomethyl-1,3-dioxolane (XDXL), wherein XDXL is 2-chloromethyl-1,3-dioxolane (CDXL ) or 2-bromomethyl-1,3-dioxolane (BDXL).

Further, the catalyst in the first step is a Lewis acid or a protonic acid, the Lewis acid includes boron trifluoride etherate or trifluoromethanesulfonic acid, and the protonic acid includes tetrafluoroboric acid or trifluoromethanesulfonic acid Acetic acid etc.

Further, the initiator in the first step is a diol, and the diol includes 1,4-butanediol, ethylene glycol or neopentyl glycol; the reaction solvent in the first step is a chlorinated alkane , the chlorinated alkanes include dichloromethane, chloroform or 1,2-dichloroethane.

Further, the molar ratio of the catalyst and the initiator in the first step is 0.05:1-2:1; the molar ratio of the initiator and the monomer is 1:10-1:150.

Furthermore, the temperature of the polymerization reaction in the first step is -20-60° C., and the polymerization reaction time is 6-48 hours.

Further, the azide reagent in the second step is sodium azide, and the molar ratio of sodium azide to halogen atoms in the carbon-halogen bond is 1.1:1˜5:1.

Further, the catalyst in the second step is a crown ether compound or a quaternary ammonium compound, the crown ether compound includes 15 crown 5 or 18 crown 6, and the quaternary ammonium compound includes tetrabutylammonium bromide or Dodecylbenzyltrimethylammonium chloride, amphiphilic polymers including PEG.

Further, the reaction solvent in the second step is a dipolar aprotic polar solvent, and the dipolar aprotic polar solvent includes dimethylformamide (DMF), dimethylacetamide (DMAC) or dimethyl Disulfoxide (DMSO).

Further, the reaction temperature in the second step is 70-150° C., and the reaction time is 6-48 hours.

Beneficial effects of the present invention: (1) The nitrogen content of poly 2-azidomethyl-1,3-dioxolane (PADXL) is close to that of PAMMO, and the azide polymer with high oxygen content and high flexibility at the terminal hydroxyl group is similar to that of PAMMO. The oxygen content is close to twice that of PAMMO. When PADXL is used as a binder, it is more conducive to the complete combustion of the formulation components, has a higher calorific value and is conducive to maintaining the oxygen balance of the formulation. (2) Compared with PAMMO in terms of molecular structure, the side chain of PADXL has one less methyl group and one more oxygen atom in the main chain. Therefore, when used as an adhesive, the increase in the number of atoms carried by the main chain will lead to better mechanical properties ; At the same time, oxygen atoms are added to the main chain, so that the flexibility of the main chain is better, and it will have a lower glass transition temperature and low-temperature mechanical properties. (3) The high flexibility of the main chain of PADXL will reduce its viscosity and have better processing performance. (4) The number-average molecular weight of the hydroxyl-terminated azide polymer with high oxygen content and high flexibility synthesized by the present invention is 1000-20000, the nitrogen content can reach more than 31.5%, the oxygen content can reach more than 24%, and the glass transition temperature is low at -50°C.

Description of drawings

Fig. 1 is a synthesis route of poly 2-azidomethyl-1,3-dioxolane (PADXL), a highly flexible azide polymer with high oxygen content at the terminal hydroxyl group of the present invention.

Fig. 2 is the H NMR spectrum of the polymer synthesized in Example 1 of the present invention.

Fig. 3 is the GPC curve of the polymer synthesized in Example 1 of the present invention.

Fig. 4 is the DSC curve of the polymer synthesized in Example 1 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following examples are only used to illustrate the present invention rather than limit the scope of the present invention, and those skilled in the art can make some non-essential improvements and adjustments based on the content of the above invention.

Example 1

The synthesis method of the azide polymer with high oxygen content and high flexibility at the terminal hydroxyl group of this embodiment is as follows:

(1) In a four-neck flask equipped with mechanical stirring, nitrogen conduit and constant pressure dropping funnel, add initiator: 0.9g of 1,4-butanediol, reaction solvent: 40mL of dichloromethane, catalyst: Boron trifluoride ether solution 2.5mL, stirred at room temperature for 1 hour. At 50° C., 37 g of 2-chloromethyl-1,3-dioxolane (CDXL) was added dropwise, and the dropwise addition was completed within 3 hours. After 6 hours of polymerization, it was poured into methanol for precipitation, and vacuum-dried to obtain 22.6 g of poly-2-chloromethyl-1,3-dioxolane (PCDXL);

(2) In a three-neck flask equipped with a mechanical stirrer, a condenser, and a nitrogen conduit, add 12.25 g of PCDXL, 7.2 g of sodium azide, solvent: 100 mL of DMF, and catalyst: 1.32 g of 18-crown 6. Under stirring, react at 100° C. for 24 hours, pour into methanol to precipitate, filter and dry to obtain 10.3 g of hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane (PADXL). The number average molecular weight is 3500, the molecular weight distribution index ID=1.34, the functionality is 1.94, the nitrogen content is 31.9%, the oxygen content is 25.0%, and the glass transition temperature is -55.1°C.

Example 2

The synthesis method of the azide polymer with high oxygen content and high flexibility at the terminal hydroxyl group of this embodiment is as follows:

(1) In a four-neck flask equipped with mechanical stirring, nitrogen conduit and constant pressure dropping funnel, add initiator: 0.9 g of 1,4-butanediol and reaction solvent: 1,2-dichloroethane in sequence at room temperature 100 mL of alkanes, catalyst: 0.57 g of trifluoroacetic acid, and stirred at room temperature for 1 hour. At 0°C, 98 g of 2-chloromethyl-1,3-dioxolane (CDXL) was added dropwise, and the dropwise addition was completed within 3 hours. After 24 hours of polymerization, it was poured into methanol for precipitation, and vacuum-dried to obtain 83.3 g of poly 2-chloromethyl-1,3-dioxolane (PCDXL).

(2) In the three-necked flask equipped with mechanical stirring, condenser, and nitrogen conduit, add PCDXL 12.25g, sodium azide 9.75g, solvent: DMF100mL, catalyst: 3.54g of dodecylbenzyltrimethyl ammonium chloride. Under stirring, react at 70° C. for 48 hours, pour into methanol to precipitate, filter and dry to obtain 11.1 g of hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane (PADXL). The number average molecular weight is 9100, the molecular weight distribution index ID=1.68, the functionality is 1.87, the nitrogen content is 32.0%, the oxygen content is 24.7%, and the glass transition temperature is -52.2°C.

Example 3

The synthesis method of the azide polymer with high oxygen content and high flexibility at the terminal hydroxyl group of this embodiment is as follows:

(1) In a four-neck flask equipped with mechanical stirring, nitrogen conduit and constant pressure dropping funnel, add initiator: 0.62 g of ethylene glycol, reaction solvent: 85 mL of dichloromethane, catalyst: 0.88 tetrafluoroboric acid g, stirred at room temperature for 1 hour. 83.5 g of 2-bromomethyl-1,3-dioxolane (BDXL) was added dropwise at room temperature, and the addition was completed within 3 hours. After 12 hours of polymerization, it was poured into methanol for precipitation, and vacuum-dried to obtain 75g of poly-2-bromomethyl-1,3-dioxolane (PBDXL);

(2) Add 16.7g of PBDXL, 13g of sodium azide, solvent: 100mL of DMSO, and catalyst: 3.54g of 15 crown 5 into a three-neck flask equipped with mechanical stirring, a condenser, and a nitrogen conduit. Under stirring, react at 90° C. for 30 hours, pour into methanol to precipitate, filter and dry to obtain 11.4 g of hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane (PADXL). The number average molecular weight is 6600, the molecular weight distribution index ID=1.51, the functionality is 1.9, the nitrogen content is 31.8%, the oxygen content is 24.8%, and the glass transition temperature is -53.7°C.

Example 4

The synthesis method of the azide polymer with high oxygen content and high flexibility at the terminal hydroxyl group of this embodiment is as follows:

(1) In a four-neck flask equipped with mechanical stirring, nitrogen conduit and constant pressure dropping funnel, add initiator: 0.62 g of ethylene glycol, reaction solvent: 190 mL of chloroform, catalyst: trifluoromethanesulfonic acid in sequence at room temperature 0.075g, stirred at room temperature for 1 hour. 184 g of 2-bromomethyl-1,3-dioxolane (BDXL) was added dropwise at -20°C, and the dropwise addition was completed within 3 hours. After 48 hours of polymerization, it was poured into methanol for precipitation, and vacuum-dried to obtain 145g of poly-2-bromomethyl-1,3-dioxolane (PBDXL);

(2) Add 16.7g of PBDXL, 19.5g of sodium azide, solvent: DMAC 100mL, and catalyst: 0.5g of PEG200 into a three-neck flask equipped with mechanical stirring, condenser, and nitrogen conduit. Under stirring, react at 110° C. for 20 hours, pour into methanol to precipitate, filter and dry to obtain 10.7 g of hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane (PADXL). The number average molecular weight is 13700, the molecular weight distribution index ID=1.84, the functionality is 1.89, the nitrogen content is 32%, the oxygen content is 24.3%, and the glass transition temperature is -51.3°C.

Example 5

The synthesis method of the azide polymer with high oxygen content and high flexibility at the terminal hydroxyl group of this embodiment is as follows:

(1) In a four-neck flask equipped with mechanical stirring, nitrogen conduit and constant pressure dropping funnel, add initiator: neopentyl glycol 1.04g, reaction solvent: methylene chloride 20mL, catalyst: trifluorinated Boron ether solution 0.25mL, stirred at room temperature for 1 hour. At 40° C., 18.3 g of 2-chloromethyl-1,3-dioxolane (CDXL) was added dropwise, and the dropwise addition was completed within 3 hours. After 18 hours of polymerization, it was poured into methanol for precipitation, and dried in vacuum to obtain 16.5 g of poly 2-chloromethyl-1,3-dioxolane (PCDXL) 2

(2) Add 12.25g of PCDXL, 26g of sodium azide, solvent: 100mL of DMSO, and catalyst: 3.2g of tetrabutylammonium bromide into a three-neck flask equipped with mechanical stirring, condenser, and nitrogen conduit. Under stirring, react at 130° C. for 12 hours, pour into methanol to precipitate, filter and dry to obtain 11.8 g of hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane (PADXL). The number average molecular weight is 2000, the molecular weight distribution index ID=1.22, the functionality is 1.96, the nitrogen content is 32.4%, the oxygen content is 24.9%, and the glass transition temperature is -57°C.

Example 6

The synthesis method of the azide polymer with high oxygen content and high flexibility at the terminal hydroxyl group of this embodiment is as follows:

(1) In a four-neck flask equipped with mechanical stirring, nitrogen conduit and constant pressure dropping funnel, add initiator: neopentyl glycol 1.04g, reaction solvent: 1,2-dichloroethane 180mL at room temperature, Catalyst: 0.15 g of trifluoromethanesulfonic acid, stirred at room temperature for 1 hour. At 30° C., 172 g of 2-chloromethyl-1,3-dioxolane (CDXL) was added dropwise, and the dropwise addition was completed within 3 hours. After 36 hours of polymerization, it was poured into methanol for precipitation, and vacuum-dried to obtain 143g of poly 2-chloromethyl-1,3-dioxolane (PCDXL);

(2) Add 12.25g of PCDXL, 32.5g of sodium azide, solvent: DMAC 100mL, and catalyst: 1.6g of tetrabutylammonium bromide into a three-neck flask equipped with mechanical stirring, condenser, and nitrogen conduit. Under stirring, react at 150° C. for 6 hours, pour into methanol to precipitate, filter and dry to obtain 12 g of hydroxyl-terminated poly 2-azidomethyl-1,3-dioxolane (PADXL). The number average molecular weight is 17100, the molecular weight distribution index ID=2.12, the functionality is 1.91, the nitrogen content is 31.7%, the oxygen content is 24.7%, and the glass transition temperature is -50.4°C.

Table 1 Comparison of molecular formula, nitrogen content and oxygen content between PADXL and PAMMO

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. A method for synthesizing a hydroxyl-terminated high-oxygen-content high-flexibility azide polymer is characterized by adopting an indirect two-step method:

the first step is a cationic ring-opening polymerization: adding an initiator, a catalyst, a reaction solvent and a monomer into a reaction container, reacting the initiator with the catalyst to release hydrogen ions, attacking oxygen atoms rich in electrons in the monomer by the hydrogen ions, inducing the monomer to open a ring, and carrying out a polymerization reaction at a certain temperature to obtain a polymer;

the second step is an azide reaction: carrying out substitution reaction on a nitridizing reagent and halogen atoms in carbon-halogen bonds on the side chain of the polymer prepared in the first step in a dipolar solvent under the action of a catalyst to obtain a nitridized polymer with high oxygen content and high flexibility of terminal hydroxyl groups;

the monomer in the first step is 2-chloromethyl-1,3-dioxolane or 2-bromomethyl-1,3-dioxolane.

2. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer according to claim 1, wherein the method comprises the following steps: the catalyst in the first step is Lewis acid or protonic acid, the Lewis acid comprises boron trifluoride diethyl etherate or trifluoromethyl sulfonic acid, and the protonic acid comprises tetrafluoroboric acid or trifluoroacetic acid.

3. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer as claimed in claim 1, wherein the method comprises the following steps: the initiator in the first step is a diol comprising 1,4-butanediol, ethylene glycol or neopentyl glycol; the reaction solvent in the first step is chloroalkane, and the chloroalkane comprises dichloromethane, chloroform or 1,2-dichloroethane.

4. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer according to claim 1, wherein the method comprises the following steps: the molar ratio of the catalyst to the initiator in the first step is 0.05 to 2:1; the molar ratio of the initiator to the monomer is 1.

5. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer according to claim 1, wherein the method comprises the following steps: the temperature of the polymerization reaction in the first step is-20 to 60 ℃, and the polymerization reaction time is 6 to 48 hours.

6. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer according to claim 1, wherein the method comprises the following steps: in the second step, the nitridizing reagent is sodium nitridizing, and the molar ratio of the sodium nitridizing to halogen atoms in the carbon-halogen bond is 1.1 to 5:1.

7. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer according to claim 1, wherein the method comprises the following steps: the catalyst in the second step is crown ether compound or quaternary ammonium salt compound, the crown ether compound comprises 15 crown 5 or 18 crown 6, the quaternary ammonium salt compound comprises tetrabutyl ammonium bromide or dodecyl benzyl trimethyl ammonium chloride, and the amphiphilic polymer comprises PEG.

8. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer according to claim 1, wherein the method comprises the following steps: the reaction solvent in the second step is a dipolar aprotic polar solvent including dimethylformamide, dimethylacetamide or dimethylsulfoxide.

9. The method for synthesizing the hydroxyl-terminated high-oxygen-content high-flexibility azide polymer according to claim 1, wherein the method comprises the following steps: the reaction temperature in the second step is 70-150 ℃, and the reaction time is 6-48 hours.

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